News reports typically characterize the Syrian rebellion as being 16 or 17 months old. It is one of those descriptions delivered en passant while relating the news of the day: the battle for Aleppo grinds on into its sixth day threatening a massive humanitarian crisis; new video shows rebels executing unarmed prisoners; President Bashar Assad urges his troops on through written messages but declines to make public appearances, and so on. But the International Crisis Group (ICG), a respected organization of analysts, mediators and former diplomats, on Wednesday issued a report urging opponents of the Assad regime, both Syrian and international, to pay closer attention to the implications of that 17-month time span.

Not only has the Assad regime survived an unprecedented assault, the ICG argues, but it also is no longer the Assad regime of February 2011 — and the rebellion challenging it also may have morphed into something quite different from the uprising that began last year. As a result, stakeholders looking to end the crisis are in urgent need of some thinking that goes beyond speculating whether Assad will go the way of Libya’s Muammar Gaddafi, Yemen’s Ali Abdullah Saleh, or any other autocrat felled during the past year’s Arab rebellion. Syria’s trajectory will be very different. Says the ICG report:

Perhaps the most significant and least appreciated is what, over time, has become of the regime. The one that existed at the outset of the conflict almost certainly could not have survived the spectacular killing of top officials in the heart of its traditional stronghold; street combat in Damascus, Aleppo and a string of other towns; the loss of important border crossings with Turkey and Iraq; all amid near-total economic devastation and diplomatic opprobrium. That, a year and a half later, its new incarnation not only withstood those blows but vigorously counterpunched sends a message worthy of reflection.

Assad’s regime, it warns, is morphing into something less like a government and more akin to factional militia locked into an increasingly brutal fight for its collective survival, relying on an Alawite community that sees a rebel triumph as nothing less than a mortal threat.

[The regime] is mutating in ways that make it impervious to political and military setbacks, indifferent to pressure and unable to negotiate. Opposition gains terrify Alawites, who stand more firmly by the regime’s side. Defections solidify the ranks of those who remain loyal. Territorial losses can be dismissed for the sake of concentrating on “useful” geographic areas. Sanctions give rise to an economy of violence wherein pillaging, looting and smuggling ensure self-sufficiency and over which punitive measures have virtually no bearing. That the regime has been weakened is incontrovertible. But it has been weakened in ways that strengthen its staying power.

The rebel campaign in Aleppo was, by some rebel accounts, an attempt to create a “safe haven” that would encompass Syria’s largest city, and its commercial hub, and stretch all the way to the Turkish border. That would not only allow armaments to be delivered more freely from Turkey but would also create a beachhead on which rebels could proclaim an alternative political authority that could then be recognized by foreign powers as Syria’s legitimate government. Clearly, foreign backers were hoping for that outcome — Secretary of State Hillary Clinton last week even predicted the emergence, soon, of a “safe haven” for anti-Assad forces in Syria — which is modeled loosely on Libya. There, it was after rebels had taken control of the eastern city of Benghazi and proclaimed an alternative government, that NATO intervened ostensibly to protect them from being overrun but then waged an offensive air campaign to take down Gaddafi. The emergence of a rebel-controlled zone in Syria would certainly have raised pressure on Western governments to provide direct military support to defend it.

So far, that outcome isn’t looking likely. Not only are Syria’s rebel military and political groupings far more diverse and divided than their Libyan counterparts were, but the city of Aleppo itself appears to be divided between supporters and opponents of the rebellion. Large sections of the civilian population, particularly middle-class and wealthier residents, and also its Christian community, are hostile to the presence of rebel fighters in their city, even if they might be politically opposed to Assad.

If, as is expected, the superior armaments of the regime’s forces see them prevail in the current battle for Aleppo, that would reinforce a sense of strategic stalemate: the regime is unable to bludgeon the rebellion into submission, and it has lost control of large swaths of rural Syria to an insurgency capable of fighting on a number of fronts but that is unable to muster a knockout blow.

The evolution of the protest movement that began early in 2011 into a full-blown civil war involving actors ranging from the U.S., Turkey, Saudi Arabia and al-Qaeda to Russia and Iran, has probably done more to strengthen the regime’s core and its determination to fight to the end than it has done to create a soft-landing. To the extent that the Alawites believe the triumph of the rebellion consigns them to a grim fate, they will fight to prevent that — with the tacit backing of many in other minorities and sections of society that feel threatened by the prospect of a victory by the hard men, many of them Islamists, who fight under the banner of the loose-knit Free Syrian Army. Video imagery touted by the rebels of the summary execution of a group of Aleppo men accused of abuses on behalf of the regime doesn’t do much to ease such fears. And the sectarian undertow that grows stronger as the fight drags on works to Assad’s advantage. The rebellion may have forced the regime to relinquish control of large swaths of territory, even the sovereign control of some of Syria’s border crossings, but in doing so it has, if anything, reinforced the determination of Assad’s core supporters to fight on.

If the regime has, indeed, rendered itself immune to traditional levers of statecraft, the push to pressure Russia and China to back new economic punishments for the regime will have limited impact. And seeking to prevail militarily almost guarantees a protracted fight:

There can be nothing more to expect from a regime that, by its very nature — never much of an institutionalised state, no longer genuinely a political entity — has ceased being in a position to compromise, respond to pressure or inducement or offer a viable solution. Which means that the traditional international panoply of actions, from public blandishments to condemnation, from threats to sanctions, is not about to work.

Preventing Syria’s descent into a generational civil war may now depend on the ability of the Syrian opposition to change the dynamic that keeps Alawites fighting for Assad as if their lives depended on it. A convincing repositioning of the rebellion on inclusive terms will be tough, especially given the bitterness of the fight so far and the divisions among the various parties. But absent the emergence of an alternative that coffers the Alawites and other regime supporters a place in the post-Assad sun, the morbid spectacle of urban combat in Syria could drag on for months, even years.

Tony Karon is a senior editor at TIME, where he has covered international conflicts in the Middle East, Asia, and the Balkans since 1997. A native of South Africa, he now resides with his family in Brooklyn, New York.